Suresh Maniyarasu

Helmholtz-Zentrum Berlin für Materialien und Energie

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Andrew G. Thomas

University of Manchester

Wendy R. Flavell

University of Manchester

Ben F. Spencer

University of Manchester

Hongbo Mo

University of Hong Kong

Philippe Holzhey

University of Oxford

David J. H. Cant

National Physical Laboratory

Alexander G. Shard

National Physical Laboratory

Steve Albrecht

Technische Universität Berlin

Matthew R. Leyden

Helmholtz-Zentrum Berlin für Materialien und Energie

Lars Korte

Helmholtz-Zentrum Berlin für Materialien und Energie

Cooperative Institutions

University of Manchester

Helmholtz-Zentrum Berlin für Materialien und Energie

Henry Royce Institute

Chinese Academy of Sciences

Ningbo Institute of Industrial Technology

Photonic Science (United Kingdom)

International Advanced Research Centre for Powder Metallurgy and New Materials

Science Oxford

University of Oxford

Technical University of Denmark

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Inelastic background modelling applied to hard X-ray photoelectron spectroscopy of deeply buried layers: A comparison of synchrotron and lab-based (9.25 keV) measurements

Applied Surface Science (2020)

Ben F. Spencer Suresh Maniyarasu Benjamen P. Reed David J. H. Cant Ruben Ahumada‐Lazo

Hard X-ray Photoelectron Spectroscopy (HAXPES) provides minimally destructive depth profiling into the bulk, extending the photoelectron sampling depth. Detection of deeply buried layers beyond the elastic limit is enabled through inelastic background analysis. To test the robustness of this technique, we present results on a thin (18 nm) layer of metal–organic complex buried up to 200 nm beneath organic material. Overlayers with thicknesses 25–140 nm were measured using photon energies ranging 6–10 keV at the I09 end station at Diamond Light Source, and a new fixed energy Ga Kα (9.25 keV) laboratory-based HAXPES spectrometer was also used to measure samples with overlayers up to 200 nm thick. The sampling depth was varied: at Diamond Light Source by changing the photon energy, and in the lab system by performing angle-resolved measurements. For all the different overlayers and sampling depths, inelastic background modelling consistently provided thicknesses which agreed, within reasonable error, with the ellipsometric thickness. Relative sensitivity factors were calculated, and these factors consistently provided reasonable agreement with the expected nominal stoichiometry, suggesting the calculation method can be extended to any element. These results demonstrate the potential for the characterisation of deeply buried layers using synchrotron and laboratory-based HAXPES.

Photon energy

10.1016/j.apsusc.2020.148635

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Citations (45)

Laser Processing of KBr‐Modified SnO₂ for Efficient Rigid and Flexible Ambient‐Processed Perovskite Solar Cells

Solar RRL (2022)

Hongbo Mo Qian Chen Dong Wang Dongxu Cheng Suresh Maniyarasu

A combination of KBr modification and laser processing is utilized to prepare SnO 2 films for rigid and flexible perovskite solar cells (PSCs). The KBr modification effectively passivates the defects at the interface between SnO 2 and perovskite as well as grain boundaries of the perovskite film. A power conversion efficiency (PCE) of 20.14% is achieved with the KBr‐modified SnO 2 for the rigid PSCs fabricated under a relative humidity of around 65–75%, compared to the pristine SnO 2 films with a PCE of 18.66%. Then, a picosecond ultraviolet laser is employed to process KBr‐modified SnO 2 films on flexible substrates with a rapid scanning rate of 100 mm s −1 . The laser process improves the PCEs and durability of the PSCs. The flexible PSCs fabricated by the laser remain over 80% of their initial PCEs after 1000 bending cycles, higher than those fabricated by the hot plate showing 40% of their initial PCEs after the same bending cycles.

Ultraviolet

10.1002/solr.202200798

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Seed Layers for Wide-Band Gap Coevaporated Perovskite Solar Cells: CsCl Regulates Band Gap and Reduces Process Variability

ACS Energy Letters (2024)

Viktor Škorjanc Aleksandra Miaskiewicz Marcel Roß Suresh Maniyarasu Stefanie Severin

Coevaporation, an up-scalable deposition technique that allows for conformal coverage of textured industrial silicon bottom cells, is particularly suited for application in perovskite-silicon tandem solar cells (PSTs). However, research on coevaporated perovskites with an appropriate band gap for PSTs remains limited, with lower efficiency and reproducibility than solution-processed films. Here, we present a simple approach using a thin layer of a precursor material, namely, PbI2, PbCl2, CsI, or CsCl, as a seed layer on the hole-transporting layer/perovskite interface. We find CsCl to be the optimal seed layer for our system. Perovskite single junction cells prepared with CsCl seed layer exhibit 19.6% power conversion efficiency with a band gap of 1.69 eV and improved long-term stability. We attribute the observed enhancements to the more precise and consistent incorporation of the organic precursor into the perovskite lattice during the film growth. This work demonstrates that engineering the substrate surface is crucial for achieving well-controlled growth of efficient and stable coevaporated wide-band gap perovskite solar cells.

10.1021/acsenergylett.4c02173

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Citations (2)

Temperature dependence of MAPbI3 films by quasi-vapor deposition technique and impact on photovoltaic performance and stability of perovskite solar cells

Journal of Alloys and Compounds (2021)

Vijendar Reddy P Suresh Maniyarasu Reshma Dileep K Ramya Krishna Battula P. Uday Bhaskar

Deposition

10.1016/j.jallcom.2021.161448

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Laser-Assisted Ultrafast Fabrication of Crystalline Ta-Doped TiO₂ for High-Humidity-Processed Perovskite Solar Cells

ACS Applied Materials & Interfaces (2022)

Hongbo Mo Dong Wang Qian Chen Wei Guo Suresh Maniyarasu

A titanium dioxide (TiO2) compact film is a widely used electron transport layer (ETL) for n-i-p planar perovskite solar cells (PSCs). However, TiO2 sufferers from poor electrical conductivity, leading to high energy loss at the perovskite/ETL/transparent conductive oxide interface. Doping the TiO2 film with alkali- and transition-metal elements is an effective way to improve its electrical conductivity. The conventional method to prepare these metal-doped TiO2 films commonly requires time-consuming furnace treatments at 450-600 °C for 30 min to 3 h. Herein, a rapid one-step laser treatment is developed to enable doping of tantalum (Ta) in TiO2 (Ta-TiO2) and to simultaneously induce the crystallization of TiO2 films from its amorphous precursor to an anatase phase. The PSCs based on the Ta-TiO2 films treated with the optimized fiber laser (1070 nm) processing parameters (21 s with a peak processing temperature of 800-850 °C) show enhanced photovoltaic performance in comparison to that of the device fabricated using furnace-treated films at 500 °C for 30 min. The ambient-processed planar PSCs fabricated under high relative humidity (RH) of 50-70% display power conversion efficiencies (PCEs) of 18.34% and 16.04% for devices based on Cs0.1FA0.9PbI3 and CH3NH3PbI3 absorbers, respectively. These results are due to the improved physical and chemical properties of the Ta-TiO2 films treated by the optimal laser process in comparison to those for the furnace process. The laser process is rapid, simple, and potentially scalable to produce metal-doped TiO2 films for efficient PSCs.

10.1021/acsami.1c24225

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Loading Precursors into Self‐Assembling Contacts for Improved Performance and Process Control in Evaporated Perovskite Solar Cells

Solar RRL (2024)

Matthew R. Leyden Viktor Škorjanc Aleksandra Miaskiewicz Stefanie Severin Suresh Maniyarasu

Organo‐lead‐halide perovskites are promising materials for solar cell applications with efficiencies now exceeding 26% for single junction, and over 33% for silicon tandem devices. Evaporation has proven viable for industrial scale‐up but presents challenges for perovskite materials. Perovskite precursor is introduced into self‐assembling MeO‐2PACz hole transport layers for application to 4 source perovskite coevaporation. This allows precursors that can be difficult to add via evaporation, like methylammonium chloride. These precursor molecules influence growth during evaporation, film behavior during annealing as measured by photoluminescence, and aid the conversion to perovskite as shown by X‐Ray diffraction. Devices have improved power conversion efficiency and stability compared to a control sample within the same evaporation. The best cells reach ≈21% efficiency and comparable performing ≈20% cells maintain their original efficiency after 1000 h of maximum power tracking at 25 °C. This process provides significant process flexibility for perovskite evaporation and requires no additional steps.

10.1002/solr.202400575

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Citations (1)

Surface stability of ionic-liquid-passivated mixed-cation perovskite probed with in situ photoelectron spectroscopy

Journal of Materials Chemistry A (2022)

Suresh Maniyarasu Ben F. Spencer Hongbo Mo Alex S. Walton Andrew G. Thomas

A passivation treatment is proposed that improves perovskite photovoltaic device performance and stability to annealing in dry environments. A rationale is presented for the observed loss of stability on heating in wet environments.

Passivation

10.1039/d2ta03748c

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Citations (22)

Characterization of buried interfaces using Ga Kα hard X-ray photoelectron spectroscopy (HAXPES)

Faraday Discussions (2022)

Ben F. Spencer Stephen A. Church Paul M. Thompson David J. H. Cant Suresh Maniyarasu

The extension of X-ray photoelectron spectroscopy (XPS) to measure layers and interfaces below the uppermost surface requires higher X-ray energies and electron energy analysers capable of measuring higher electron kinetic energies. This has been enabled at synchrotron radiation facilities and by using lab-based instruments which are now available with sufficient sensitivity for measurements to be performed on reasonable timescales. Here, we detail measurements on buried interfaces using a Ga Kα (9.25 keV) metal jet X-ray source and an EW4000 energy analyser (ScientaOmicron GmbH) in the Henry Royce Institute at the University of Manchester. Development of the technique has required the calculation of relative sensitivity factors (RSFs) to enable quantification analogous to Al Kα XPS, and here we provide further substantiation of the Ga Kα RSF library. Examples of buried interfaces include layers of memory and energy materials below top electrode layers, semiconductor heterostructures, ions implanted in graphite, oxide layers at metallic surfaces, and core-shell nanoparticles. The use of an angle-resolved mode enables depth profiling from the surface into the bulk, and is complemented with surface-sensitive XPS. Inelastic background modelling allows the extraction of information about buried layers at depths up to 20 times the photoelectron inelastic mean free path.

Electron spectroscopy

Characterization

10.1039/d2fd00021k

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Citations (7)

Role of Alkali Cations in Stabilizing Mixed-Cation Perovskites to Thermal Stress and Moisture Conditions

ACS Applied Materials & Interfaces (2021)

Suresh Maniyarasu Chun-Ren Ke Ben F. Spencer Alex S. Walton Andrew G. Thomas

Perovskite solar cells (PSCs) based on organic–inorganic hybrid perovskites containing a small fraction of substituted alkali-metal cations have shown remarkable performance and stability. However, the role of these cations is unclear. The thermal- and moisture-induced degradation of FA1–xCsxPbI3 and (FA1–xCsx)1–yRbyPbI3 (where FA represents formamidinium, x, y = 0.1, 0.05) is investigated using in situ photoelectron spectroscopy (PES). Both compositions exhibit superior moisture stability compared with methylammonium lead iodide under 9 mbar of water vapor. Ga Kα hard X-ray PES is used to investigate the composition of the perovskites at depths up to 45 nm into the surface. This allows more accurate quantification of the alkali-metal distribution than is possible using conventional X-ray PES. The addition of RbI results in a fairly homogeneous distribution of both Cs+ and Rb+ in the surface layers (in contrast to surface Cs depletion seen in its absence), together with a marked reduction in surface iodide vacancies. Overall, RbI is found to play a critical role in increasing the thermal stability of FA1–xCsxPbI3 by providing a source of I– that fills iodine vacancy sites in the perovskite lattice, while Rb+ is not substantially incorporated into the perovskite. We suggest that the concomitant increase in ion migration barriers in the surface layers is key to improved PSC performance and long-lasting stability.

Formamidinium

Thermal Stability

10.1021/acsami.1c10420

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Citations (20)